This specification claims priority to German Patent Application No. 100 45 358.9, filed on Sep. 14, 2000, entitled xe2x80x9cSpot-Type Disc Brake and Associated Brake Pad With a Retaining Device for the Brake Pad.
The present invention relates to a spot-type disc brake for automotive vehicles and an associated brake pad with a retaining device for the brake pad according to the preamble of patent claim 1.
A generic spot-type disc brake with a retaining device for a brake pad is disclosed in DE 43 18 744 C1. The spot-type disc brake for automotive vehicles described in this patent comprises a floating caliper with two brake pads which are each slidably guided and supported on a brake carrier that is integrated in the steering knuckle of the automotive vehicle. The floating caliper includes a hydraulic actuating unit with a brake piston for the direct application of the first brake pad, while the second brake pad, upon brake actuation, is moved in a known fashion by axial displacement of the floating caliper indirectly into abutment with a brake disc that rotates inbetween the brake pads. The brake pads are secured to the brake piston or floating caliper by way of combined spring elements, on the one side, and clamped with respect to the brake carrier, on the other side. The piston-side brake pad is retained axially and pressed radially against the brake carrier by means of the spring element with respect to the brake disc. The radial and tangential clamping engagement of the spring element in the piston causes undesirable transverse forces on the brake piston which tilt the latter and, thus, cause disadvantageous friction forces during piston movement. Further, manufacturing tolerances may result in an offset positioning in a circumferential direction of the brake pad and the actuating unit. This means there result further undesirable transverse forces on the piston. This causes a loss in clearance which is responsible for washouts on the brake disc and, hence, undesirable brake torque variations. The result of such brake torque variations is, for example, the occurrence of undesirable vibrations such as torsional vibrations of the steering wheel which may lead to low-frequent humming noise.
Further, it is known from DE 196 17 373 C2 to secure the piston-side brake pad to the brake piston by way of a mounting element which is fixed with a limited clearance to the brake pad vertically to the axial direction. Due to the limitation of this clearance, the brake piston is, however, also in this arrangement loaded with a force vertically relative to the axial direction because the mounting element also applies a radial force component to the brake pad. Resulting therefrom are the undesirable tilting moments that act on the brake piston (as described hereinabove) and impair the piston""s free slidability in the actuating unit.
In view of the above, an object of the present invention is to provide a retaining device for a brake pad of a spot-type disc brake which provides for the brake pad both an attachment to an actuating means, e.g. a brake piston, and a clamping engagement with a pad mounting support, without exerting a force to the actuating means vertically relative to the actuating direction.
In accordance with this invention, the retaining device for the brake pad which is slidably guided and supported in a pad mounting support of the spot-type disc brake comprises two separate spring means which both together are attached to the brake pad. With respect to an associated brake disc, the brake pad is clamped axially with the actuating means by way of a first spring means, and is clamped with the pad mounting support by way of a second spring means vertically to the axial direction.
The double function of the retaining device for the piston-side brake pad is removed by the use of two spring means which operate independent in their effect. The first spring means ensures the axial attachment of the brake pad to the actuating means, especially the brake piston of an actuating device, while the second spring means clamps the brake pad radially relative to the pad mounting support. The actuating means is not influenced by the force of the second spring means.
An improvement of the spot-type disc brake with a retaining device is achieved in that the first spring means is secured with a clearance to the brake pad vertically to the axial direction or actuating direction. The result is that the force components of the two spring means are generally uninfluenced by one another, and no undesirable force effect occurs on the actuating means, especially the brake piston, due to the spring means.
A favorable embodiment of the spot-type disc brake with a retaining device is achieved because the first spring means has at least two spring arms for the abutment on the actuating means. This allows the brake pad with retaining device to safely cling to the actuating means. Starting from the point of attachment of the spring means to the brake pad, the spring arms extend in a substantially radial direction, and they are distributed particularly evenly over a corresponding circumference. The brake pad is thereby clamped uniformly with respect to the actuating means.
The second spring means is secured to the brake pad without a clearance according to a preferred design of the retaining device. The spring means is in particular riveted to a projection of the brake pad or fixed on the brake pad in a comparable manner. With another portion the second spring means is supported on the actuating means in order to apply the desired force component to the brake pad vertically relative to the axial direction or actuating direction. To realize a low-cost version of the retaining device with a small number of components, the second spring means additionally serves as an attachment means for the first spring means. In detail, the first spring means is retained vertically to the axial direction on the brake pad by means of the second spring means by maintaining a clearance. This causes no radial forces on the actuating means, especially the brake piston.
The two spring means may especially have the configuration as simple wire springs, bow springs or leaf springs, or sheet-metal springs. Of course, still other spring materials which exhibit the above-mentioned construction features are also possible.
Retaining devices with two above-described spring means can favorably be used with brake pads which are arranged on respectively one brake piston of an actuating device. The retaining device of this invention with two separate spring means is, however, not limited to a use in connection with brake pistons. The actuating means by which a corresponding retaining device with its spring means moves into abutment may also be configured as a portion of a brake caliper or brake housing. In such a case, the associated brake pad is retained on the brake caliper by means of the retaining device.
In addition, protection is sought for a corresponding brake pad with a retaining device of the above type. The retaining device, as has already been described, serves for the detachable connection of the brake pad to an actuating means of the spot-type disc brake, the said retaining device comprising a first and a second spring means. According to the present invention, the first spring means clamps the brake pad axially to the actuating means, i.e., a brake piston, while the second spring means clamps the brake pad with respect to the actuating means vertically relative to the axial direction. The first spring means is secured with a clearance to the brake pad by means of the second spring means vertically relative to the axial direction. This permits a relative displacement between the two spring means, with the result that mutual influencing of the two spring means is prevented. Preferably, the first spring means is secured to the brake pad also with an axial clearance by means of the second spring means. In particular, the first and the second spring means are secured to the brake pad in an unrotatable fashion, with respect to a rotation about the axial direction, in order to accomplish a safe support on the brake pad. Advantageously, the first and the second spring means are unrotatably connected to each other already before they are secured to the brake pad. This simplifies handling of the two spring means in general and their assembly.